[rules-users] null checking

[vdelbart]

I think it's not in the manual.

Try this : 

seller: ( seller.cheese != null, seller.active == true )
cheese: ( this != null, cheese.type == "chedder" ) from seller.cheese

I don't kown if it's fine but it works.


dave sinclair wrote:
> 
> read the manual
> 
> http://downloads.jboss.com/drools/docs/4.0.7.19894.GA/html_single/index.html
> 
> On Thu, Oct 16, 2008 at 3:03 PM, samd <sdoyle_2 at yahoo.com> wrote:
> 
>>
>>
>>
>> samd wrote:
>> >
>> > How do I evaluate null conditions in the following case for example?
>> >
>> > seller: ( seller.cheese != null && seller.active == true )
>> > cheese: ( cheese.type == "chedder" ) from seller.cheese
>> >
>> > In the above example seller.cheese is null but seller is used in the
>> > second part of the rule since we can't evaluate facts for null for some
>> > reason how do you check for a null condition.
>> >
>> >
>>
>> should be cheese: ( type == "chedder" ) from seller.cheese
>>
>> anyways I tried doing this
>>
>> (
>>  seller: ( seller.cheese != null && seller.active == true )
>>  cheese: ( cheese.type == "chedder" ) from seller.cheese
>> )
>> or
>> (
>>  seller: ( seller.cheese = null && seller.active == true )
>> )
>> Which throws an error
>> I just need the correct syntax I guess heh
>>
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>>
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> 
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